The present invention relates to a novel basic concept for the rapid, random-access retrieval of micrographic and data images stored on plural windowed discs. The concept can be implemented to provide a variety of specific devices.
The term "windowed" disc refers to an optically clear area on each disc that characterizes this type of invention. The essential principle is that aligned windows in plural discs form a viewing column through which the stored information on any single unaligned disc may be seen.
The present invention shares some aspects of the windowed disc concept with prior art. Examples of the prior art are the patents to Braggs et al, U.S. Pat. No. 2,989,904; Irazoqui, U.S. Pat. No. 3,421,802; Booth, U.S. Pat. No. 3,959,801; Harvey, U.S. Pat. No.4,132,469 and Pick, U.S. Pat. No. 3,975,745. However, it differs greatly from the prior art in its general concept and the apparatus for implementing it.
The primary advantage of windowed disc devices over related disc devices regards the amount of space utilized between the discs, which greatly affects the overall storage density of the device. Optical retrieval devices based on the principles of magnetic disk storage devices have no window and consequently must insert read heads between discs (Booth; Pick). Providing each disc with an optically clear window allows discs to be stored proximately.
Prior windowed disc devices may be divided into two groups depending on the function performed by the disc window. In one group, the viewing column formed by the aligned windows is used to allow passage of an optical head from one disc position to another (Braggs; Harvey). In this group, the disc windows must be open at the rim in order to allow lateral insertion of the optical head into the viewing column. In the second group, the viewing column is used to allow passage of the information-reading optical beam only, which is directed from the ends of the viewing column (Irazoqui). In this group, the disc rim at the window location may be closed since no physical components are inserted into the viewing column. The present invention belongs to the latter group.
Four features of the present invention distinguish it from all other prior windowed disc art. First, it provides mechanisms that access discs containing plural concentric levels of images; all prior art windowed discs contain only a single ring of images.
Second, it provides mechanisms that address a plurality of object planes (disc positions) while maintaining a constant aerial image plane, thereby enabling retrieval with no relative motion between the disc stack, the chassis and the primary viewing element (lens, video pickup, change coupled device). Prior art devices either use a single object plane or fail to disclose means for achieving plural object planes.
Third, the present invention provides means for the simultaneous rotation of two or more discs at one time. Prior art devices find and file sequentially. That is, they rotate a selected disc to a selected position (find), then rotate it back to the aligned home position (file), then move to another disc position to find again. The present invention can find on one disc while simultaneously filing the previous disc.
Fourth, the present invention uses perimeter disc support in preferred embodiments, whereas prior art discs are all supported at their centers.
The various prior art devices have additional problems which can be solved or alleviated by the present invention. For example, the present invention can:
record as well as play;
retrieve any image in 100,000 in 1/2 second;
store more than one type of information on the same storage medium, allowing both eye-readable and machine-readable playback from the same machine;
store multiple media types (black-and-white and color photo emulsions, eraseable laser-ablative optical data disc media) on the same disc or in the same cartridge, allowing retrieval of a wide range of information types from the same machine;
avoid loss of storage area due to peripherally-increasing bit size (as required in constant-velocity disc devices);
avoid loss of storage area due to on-medium servo guidance tracks or spaces (as required by micron bit size optical disc devices);
increase stack volume-density by storing discs contigously (as cited above);
increase stack volume-density by reducing the thickness of the discs using integral constructions of transparent substrates and emulsion rather than the multi-piece opaque substrate constructions used by prior art;
facilitate the placement and removal of discs in cartridges;
interface with any type of display or transmission equipment capable of utilizing an aerial image (ocular lens, projection lens, video pickup, CCD facsimile scanner, etc.);
avoid the coding of image location on the image medium (for example, micrographic "blip" coding);
operate under total computer control of its various electromechanical components (computer-driven rather than "computer-assisted-retrieval", CAR);
store unitized volumes of information far beyond the unit capacities of existing equipment (for example, beyond the 80-image limit of carousel slide projections, beyond the 200-foot roll film cartridge capacity of current CAR micrographic systems and beyond the 500 megabyte limit of magnetic disc drives);
access large volumes of information without manual operator intervention (for example, no roll film cartridge swapping, no exchanging of magnetic disc assemblies);
largely avoid "autofocus" adjustments by maintaining precise positioning of all discs at all times; can also use its existing optical adjustment system for autofocus purposes if needed.
These and other advantages of the present invention will become more apparent with consideration of the following description.